1. Field of the Invention.
The present invention relates to a replenisher control system for use in processors of photosensitive material.
2. Description of the Prior Art
Automatic photographic film and paper processors transport sheets or webs of photographic film or paper through a sequence of processor tanks in which the photosensitive material is developed, fixed, and washed, and then transports the material through a dryer. It is well known that photographic processors require replenishment of the processing fluids to compensate for changes in the chemical activity of the fluids.
First, it has been recognized that replenishment is necessary to replace constituents used as photosensitive film or paper is developed in the processor. This replenishment is "use related" or "exhaustion" chemical replenishment. Both developer and fix solutions require exhaustion replenishment.
Second, chemical activity of the developer solution due to aerial oxidation occurs with the passage of time regardless of whether film or paper is being processed. Some replenishment of an "anti-oxidation" (A-O) replenishment solution which counteracts this deterioration.
Replenishment systems were originally manually operated. The operator would visually inspect the processed film or paper and manually operate a replenisher system as he deemed necessary. The accuracy of the manual replenisher systems was obviously dependent upon the skill and experience of the operator.
Various automatic replenishment systems have been developed for providing use-related replenishment. Examples of these automatic replenishment systems include U.S. Pat. Nos. 3,472,143 by Hixon et al; 3,529,529 by Schumacher; 3,554,109 by Street et al; 3,559,555 by Street; 3,561,344 by Frutiger et al; 3,696,728 by Hope; 3,752,052 by Hope et al; 3,787,689 by Fidelman; 3,927,417 by Kinoshita et al; 3,990,088 by Takita; 4,057,818 by Gaskell et al; 4,104,670 by Charnley et al; 4,119,952 by Takahashi et al; 4,128,325 by Melander et al; and 4,134,663 by Laar et al. Examples of prior art replenisher controls for providing both exhaustion and anti-oxidation replenishment are shown in U.S. Pat. Nos. 3,822,723 by Crowell et al and 4,174,169 by Melander et al.
In the past, test strips or control strips of photosensitive material have been processed and then evaluated for determining whether the processor is yielding processed material having the desired densities. Patents showing automatic evaluation of test strips include U.S. Pat. Nos. 3,623,418 by Ost; 3,636,851 by Furst; and 3,995,959 by Shaber.
The Ost Patent 3,623,418 describes a system in which a test strip of photographic film is transported through a developer sample chamber, where it is developed using a sample of developer fluid from the main developer tank. The developed test strip then passes between a lamp and a densitometer head, which senses the intensity of light transmitted through the test strip. The resistance of the densitometer is connected in a bridge circuit which is used to control replenishment.
The Furst U.S. Pat. No. 3,636,851 shows a film processor which includes a sensitometer for recording test information on a test prior to the test film entering the processor tanks, and a densitometer at the output end of the processor for measuring density of the processed test film. The Furst patent suggests the possibility of supplying the densiometric data in digital form to a process controller to control the entire manufacturing operation.
The Shaber U.S. Pat. No. 3,995,959 shows a processor in which a test strip includes areas of unexposed (base fog) area, light (medium density) area, and dark (high density) area. Densitometer readings are made of the processed test film and signals are generated indicating whether the base fog area is acceptable or too dark; whether the dark area is acceptable or too light; and whether the medium area is acceptable, too light, or too dark. Based upon these signals, light emitting diodes are lit to indicate the status of the film processor. The light emitting diodes indicate the following conditions: acceptable, developer underreplenished, developer temperature too low, developer overreplenished, developer temperature too high, and developer contaminated.